This research aims to investigate the relationship between the control of the human breathing pattern and the mechanical load presented to the respiratory musculature by intrinsic mechanics and by the addition of external mechanical loads, flow resistive and electric, similar in size to those encountered normally due to changes in posture, sleep state, and disease. Major goals are to provide better understanding of the way neural reflexes operate in compensation for loading, and to determine how these reflexes interact with behavioral reactions, produced subsequent to conscious perception of impeded breathing. Within this framework, the specific actions of flow resistive loading upon the control of the larynx will be investigated using a body surface loading technique designed to separate the influences of upper airway receptors from those of pulmonary stretch receptors. Influences of upper airway receptors upon the regulation of the respiratory pattern in response to mechanical loading will be assessed from experiments in which mechanical loads are presented in ways to involve or exclude loading effects from the upper airway. Interactions between subconscious reflex pattern regulation responses and behavioral reactions subsequent to perception of loading will be examined by applying loads ranging from below to well above the perceptual threshold. The effect of the state of consciousness upon respiratory pattern regulation in loading will be examined by determining the pattern responses to loads that are too small to be perceived by normal subjects and then determining the effect of sleep upon those pattern regulation response. These responses will be investigated in normal humans subjects and in patients suffering from respiratory pathologies to determine whether diseases alter patients' abilities to adapt to mechanical loads. Regulation of tonic activity in the diaphragm in response to loading will be investigated from measurement of the diaphragmatic electromyogram, since control of the tension in the diaphragm during expiration would help to regulate the end-expiratory long volume and the length of the diaphragm of the start of the next expiration, an important determinant of diaphragm performance. These studies will improve the basic understanding of how the human breathing pattern is regulated in response to mechanics, an important step in being able to effectively deal with respiratory diseases involving mechanical loads and the upper airway.